Diaphragm seals for transmitting media pressure usually comprise a diaphragm-seal body or diaphragm-carrier body having a media-side surface and a separating diaphragm, which is connected to the diaphragm-seal body in a pressure-tight manner along at least one periphery, a pressure chamber being formed between the separating diaphragm and the diaphragm-seal body in the process, wherein a channel extends from the pressure chamber through the diaphragm-seal body, and the pressure chamber and the channel are filled with a transmission fluid in order to transmit media pressure prevailing at the separating diaphragm to a pressure transducer. The pressure transducer may, for example, be a pressure-measuring cell, which is mounted between two process connection flanges, another separating diaphragm, or a capillary line connected to the channel.
Such diaphragm seals are generally used in extremely hot and cold applications in order to thermotechnically isolate the pressure transducer from the process environment. The diaphragm seal fulfills this function by isolating the pressure transducer from the process medium by means of a capillary system, which is filled with transmission fluid and installed in a cooling section.
For this purpose, constructions of diaphragm seals that comprise a variety of components are known from the prior art. These components are a capillary tube, a base body, as well as two capillary tube adapters. The long, curved capillary tube is connected at its first end to the diaphragm-carrier body by means of the first capillary tube adapter and at its second end to the pressure transducer by means of the second capillary tube adapter. Since the capillary tube has an outer diameter of only a few millimeters and is therefore not very stable mechanically, the construction is mechanically stabilized by means of a base body—generally, a U-shaped steel support—which is welded at its first end to the diaphragm-carrier body and at its second end laterally to a process connection flange. In this construction, the capillary tube is curved such that it typically has an S-shape and a first bending radius when starting from the first end and a second bending radius when starting from the second end, wherein the capillary extends essentially linearly in the U-shaped steel support in the region between the two bending radii, i.e., between the U-shaped steel support's flanges, and is thus protected. The U-shaped steel support is used for mechanical stability and is welded on the diaphragm-carrier body to its front side by hand or manually, and at the opposite end, the U-shaped steel support is welded laterally to the process connection flange along the two flanges of the U-shaped profile by hand or manually as well, in order to thus achieve an increased mechanical stability in the region of the welding in this way.
Such diaphragm seals thus require an extremely complex mechanical construction, since the diaphragm seal is made of four individual elements and, further, the U-shaped steel support must be laboriously welded to the diaphragm-carrier body and the process connection flange by hand or manually. The welding by hand or manually entails, in addition, the risk that the weld joint has small gaps or holes, since the interior of the U-shaped steel support is accessible only with difficulty during welding on the diaphragm-carrier body and/or the pressure transducer. The gaps and holes created in the weld joint in this way subsequently constitute potential corrosion starting points during the long-lasting operation of the pressure transducer (under partially extreme external weather conditions).
It is also disadvantageous in this construction that the axis of vibration of the entire system, i.e., of the diaphragm seal with the diaphragm-carrier body and the pressure-measuring cell, which is mounted between two process connection surfaces, is located at a relatively large distance from the center of gravity of the entire system. This leads to a relatively high imbalance, which results in harmful vibrations and increased wear and tear.
The diaphragm seals known from the prior art further have the disadvantage that they can only be cleaned with difficulty, since the inner regions are not easily accessible as a result of the U-shaped steel support. Specifically in the use of such pressure transducers in the fields of biotechnology and chemistry, easy cleaning is, however, of significant importance.